Novel bi-SO3H-functionalized ionic liquids based on piperazinium: Highly efficient and recyclable catalysts for the synthesis of β-acetamido ketones

A series of novel bi-SO3H-functionalized ionic liquids were synthesized and acted as catalysts for the synthesis of β-acetamido ketones. Compared with traditional single-SO3H-functionalized ionic liquids, less amount of catalysts, higher yields and shorter reaction time are the key features of this methodology. Hammett function values and the minimum-energy geometries of bi-SO3H-functionalized ILs were calculated and the results revealed that the acidities and catalytic activities of ILs in synthesis of β-acetamido ketones were influenced by their structures. The IL [(PS)2pi][OTf]2 with the shortest HO bond distance had the strongest acidity and the highest catalytic activity.

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► Several bi-SO3H-functionalized ionic liquids (BSFILs) were developed.
► BSFILs exhibited higher activities compared to single-SO3H-functionalized ILs.
► IL with shorter hydrogen bond had stronger acidity and higher catalytic activity.
► Low cost, high yields, short reaction times were the key features of this method.